Methods and Systems for Fabricating Layers of Metallic Glass-Based Materials

ABSTRACT

Systems and methods of fabricating layers of metallic glass are described. Many embodiments provide conduction quenching processes to form a metallic glass coating. In many embodiments, the systems and methods comprise applying a metallic glass forming material to form a layer on at least a portion of an object, heating up the layer of metallic glass forming alloy, and cooling the layer of metallic glass-based material to form a layer of solid phase metallic glass.

CROSS-REFERENCE TO RELATED APPLICATIONS

The current application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/118,426 entitled “Methods and Systems for Fabricating Layers of Metallic Glass-Based Materials” filed Nov. 25, 2020. The disclosure of U.S. Provisional Patent Application No. 63/118,426 is hereby incorporated by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention generally regards layers of metallic glass based materials, and techniques for fabricating such layers.

BACKGROUND OF THE INVENTION

Metallic glasses, also known as amorphous metals, have generated much interest for their potential as robust engineering materials. Metallic glasses are characterized by their disordered atomic-scale structure in spite of their metallic constituent elements—i.e. whereas conventional metallic materials typically possess a highly ordered atomic structure, metallic glasses are characterized by their disordered atomic structure. Notably, metallic glasses typically possess a number of useful material properties that can allow them to be implemented as highly effective engineering materials. For example, metallic glasses are generally much harder than conventional metals, and are generally tougher than ceramic materials. They are also relatively corrosion resistant, and, unlike conventional glass, they can have good electrical conductivity.

Nonetheless, the manufacture and implementation of metallic glasses present challenges that limit their viability as engineering materials. In particular, metallic glasses are typically formed by raising a metallic glass above its melting temperature, and rapidly cooling the melt to solidify it in a way such that its crystallization is avoided, thereby forming the metallic glass. The first metallic glasses required extraordinary cooling rates, e.g. on the order of 10⁶ K/s, to avoid crystallization, and were thereby limited in the thickness with which they could be formed because thicker parts could not be cooled as quickly. Indeed, because of this limitation in thickness, metallic glasses were initially largely limited to applications that involved coatings. Accordingly, the present state of the art can benefit from improved techniques for implementing layers of metallic glass.

BRIEF SUMMARY OF THE INVENTION

Methods and systems in accordance with embodiments of the invention provide fabricating layers of metallic glass-based materials. Many embodiments provide heating and conduction quenching processes during the fabrication of metallic-glass based materials. Several embodiments provide metallic glass-based coating layers using the fabrication processes. Some embodiments provide that the metallic-glass based coating layers have a uniform thickness throughout the coating layer. In certain embodiments, the metallic-glass based coating layers have a uniform thickness ranging from about 1 micron to about 1 mm. A number of embodiments provide the metallic-glass based coating layers have a surface roughness ranging from about 0.020 micron Ra to about 250 micron Ra.

In many embodiments, the metallic-glass forming alloys can be prepared to form the metallic glass-based coating layers. The metallic-glass forming alloys in accordance with several embodiments can have crystalline and/or amorphous structures. Examples of metallic-glass forming alloy elements include (but are not limited to): Zr, Ti, Cu, Al, Nb, Pt, Pd, Au, Ni, Fe, Mg, Ce, La, Be, P, C, B and their combinations thereof. Some embodiments provide that the metallic glass forming alloys can be in forms including (but not limited to) foils, sheets, powders, particles, granules, ribbons, and chunks. Certain embodiments provide that metallic glass forming alloy foils, sheets, and/or ribbons can form a more uniform coating layers than metallic glass forming alloy powders and/or particles.

Many embodiments provide that metallic-glass forming alloys can be coated on at least a part of an object to be coated. In several embodiments, foils of metallic-glass forming alloys can be overlaid on at least a part of an object to be coated. Some embodiments provide that the object to be coated can be placed on a heating platform including (but not limited to) a heating block. The heating block can be made of any heat conductive materials including (but not limited to) copper, brass, or steel. Several embodiments provide the heating platform can be placed above a cooling platform and below a second cooling platform. The cooling platform can include (but are not limited to) conduction cooling platform. In certain embodiments, the heating platform can be aligned in the center with the cooling platforms. The cooling platforms including (but not limited to) quench blocks can be made of any heat conductive materials including (but not limited to) copper, brass, or steel. The object can be heated on the heating platform to at least above the melting temperature of the metallic-glass forming alloys in accordance with some embodiments. The heating process in accordance with certain embodiments can be provided by a heating unit including (but not limited to) an induction heating coil. Several embodiments provide that as soon as the metallic-glass forming alloy is melted, the aligned cooling platform above can be brought in contact with the object to enable rapid cooling and formation of metallic glass-based coatings. The aligned cooling platform below the heating platform can be turned on. As the cooling platforms are aligned with the heating platform in the center, the heated object and/or the heating platform may not need to be moved around for the cooling processes. Once the metallic-glass forming alloy on the object is melted, the cooling processes can begin. In many embodiments, the cooling rate can be controlled to form various microstructures of the metallic glass-based coating layers. Examples of coating layer microstructures include (but are not limited to) fully amorphous, amorphous and crystalline, and fully crystalline.

Various embodiments are directed to methods of fabricating metallic glass including:

-   -   applying at least one layer of metallic glass forming alloy to         at least a portion of an object;     -   heating the at least one layer of metallic glass forming alloy         to at least above the melting temperature of the metallic glass         forming alloy; and     -   cooling the at least one melted layer of liquid phase metallic         glass to form a layer of solid phase metallic glass on the at         least a portion of the object;     -   wherein the cooling process is selected from the group         consisting of: conduction quenching, gas quenching, dipping in         water, dipping in oil, and dipping in molten tin.

In other various embodiments the at least one layer of metallic glass forming alloy comprises at least one element selected from the group consisting of: Zr, Ti, Cu, Al, Nb, Pt, Pd, Au, Ni, Fe, Mg, Ce, La, Be, P, C, and B.

In still other various embodiments the object is made of a material with a higher melting temperature than the melting temperature of the metallic glass forming alloy.

In yet other various embodiments the at least one layer of metallic glass forming alloy is in a form selected from the group consisting of: powder, particle, granule, chunk, foil, ribbon, and sheet.

In still yet other various embodiments the at least one layer of metallic glass forming alloy is cut to match the shape of the at least a portion of the object before applying.

In yet still other various embodiments the at least one layer of metallic glass forming alloy is heated to at least 150° C. above the melting temperature of the metallic glass forming alloy.

In still yet other various embodiments the heating is applied by a heating source selected from the group consisting of an induction heating coil, a resistive furnace, a heating lamp, a laser, an electron beam, a combustion flame, an electrical spark, and a microwave plasma.

In yet still other various embodiments the heating takes place on a heating platform comprising a heating block.

In still yet other various embodiments the heating block comprises a material selected from the group consisting of copper, brass, steel and stainless steel.

In yet still other various embodiments the conduction quenching is applied by at least one conduction quenching block, and the at least one conduction quenching block is aligned with the heating block in the center.

In still yet other various embodiments the conduction quenching is applied by two conduction quenching blocks; wherein a first conduction quenching block is above the heating block and not touching, and a second conduction quenching block is below the heating block; wherein the two conduction quenching blocks and the heating block are aligned in the center.

In yet still various other embodiments the cooling takes place immediately after the heating is complete.

In still yet various other embodiments the heating and cooling take place in vacuum.

In yet still various other embodiments the layer of solid phase metallic glass has a uniform thickness throughout the layer, and the thickness ranges from about 1 micron to about 1 millimeter.

In still yet various other embodiments the layer of solid phase metallic glass has a surface roughness ranging from about 0.020 micron Ra to about 250 micron Ra.

In yet still various other embodiments the layer of solid phase metallic glass has a microstructure selected from the group consisting of: fully amorphous, amorphous and crystalline, and fully crystalline.

Many embodiments are directed to systems for fabricating metallic glass including:

-   -   at least one heating platform;     -   at least one sample holder on the at least one heating platform;         and     -   at least one cooling block above the at least one heating         platform;     -   wherein the at least one cooling block is not touching the at         least one heating platform;     -   wherein the at least one heating platform, the at least one         sample holder, and the at least one cooling block are aligned in         the center.

Many other embodiments further include a second cooling block below the at least one heating platform, wherein the second cooling block is in contact with the at least one heating platform.

In still many other embodiments the at least one heating platform comprises a heating block comprising a material selected from the group consisting of: copper, brass, and steel.

In yet many other embodiments the at least one cooling block comprises a material selected from the group consisting of: copper, brass, and steel.

In still yet many other embodiments the second cooling block is cooled by water.

In yet still many other embodiments the at least one heating platform comprising a heating source selected from the group consisting of an induction heating coil, a resistive furnace, a heating lamp, a laser, an electron beam, a combustion flame, an electrical spark, and a microwave plasma.

Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be more fully understood with reference to the following figures, which are presented as exemplary embodiments of the invention and should not be construed as a complete recitation of the scope of the invention, wherein:

FIG. 1 illustrates a cross section of an immersion coated object in accordance with embodiments.

FIGS. 2A and 2B illustrate a surface picture and a 3D representation of a wrinkled portion of an immersion coated object in accordance with embodiments.

FIG. 3 illustrates a process for forming a layer of metallic glass in accordance with embodiments.

FIG. 4 illustrates the cross section of a thick metallic glass coating using conduction quench cooling processes in accordance with embodiments.

FIGS. 5A-5D illustrate the conduction quench cooling systems in accordance with embodiments.

FIGS. 6A-6C illustrate surface images of an object coated with metallic glass forming alloy in powder form and in foil form in accordance with embodiments.

FIGS. 7A-7D illustrate cross section images of an object coated with metallic glass forming alloy in powder form and in foil form in accordance with embodiments.

FIG. 8 illustrates Vickers hardness of metallic glass coated objects in accordance with embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to the drawings, methods and systems for fabricating layers of metallic glass-based materials are illustrated. Many embodiments implement conduction quenching processes to form metallic glass coating layers. Several embodiments provide that the metallic glass coating layers have uniform thickness throughout. In many embodiments, the systems and methods comprise applying a metallic glass forming material to form at least a layer of metallic glass-based coating material on at least a portion of an object, heating up the layer of metallic glass forming alloy, and conduction cooling the layer of metallic glass-based material to form a layer of solid phase metallic glass.

For the purpose of this invention, amorphous metal is a multi-component metal alloy that exhibits an amorphous (non-crystalline) atomic structure. These alloys can also be called metallic glasses, as they exhibit a glass transition temperature. For the purposes of this patent application, the term ‘metallic glass-based material’ shall be interpreted to be inclusive of ‘amorphous alloys’, ‘metallic glasses’, and ‘metallic glass composites’, except where otherwise noted. Metallic glass composites are characterized in that they possess the amorphous structure of metallic glasses, but they may also include crystalline phases of material within the matrix of the amorphous structure.

Crystalline phases can allow a material to have enhanced ductility, compared to where the material is entirely constituted of the amorphous structure. Many techniques can be used to implement layers of metallic glass, e.g. metallic glass coatings on objects. However, many of the techniques that have been used thus far exhibit a number of shortcomings. For example, metallic glass coating formed by thermal spray coating techniques may not be wavy but the layer can be quite rough and/or have pores. Thermal and/or plasma spray based coating processes can start with a powder material, accelerate the powder material towards a substrate by a carrier gas or various methods, and then heat the powder inside of a flame, arc, or plasma. Examples of thermal spray based techniques include high velocity oxygen fuel (HVOF), high velocity air fuel (HVAF), atmospheric plasma spray (APS), vacuum plasma spray (VPS). (See, e.g., U.S. Patent Application No. 20140010968 to C. D. Prest, et al; U.S. Pat. No. 11,078,560 B2 to J. Kang, et al.; U.S. Pat. No. 10,240,238 B2 to G. A. Croopnick; U.S. Patent Publication No. 20210198777 to J. Kang, et al.; the disclosures of which are incorporated herein by references.) However, thermal spray based coatings have suffered from problems including porous coating layers, rough coating layers, overspray, uneven coating thickness, low adhesion with the substrate, and/or oxidation of powder particles during their time in the flame or plasma.

Various sputtering based processes are used to produce produce thin metallic glass coatings. Sputtering processes include deposition spray, sputtering, physical vapor deposition, and DC magnetron sputtering. (See, e.g., U.S. Patent Application No. 20120156395 to J. C. Bilello; P. Yiu, et al., Journal of Applied Physics, 127, 030901, 2020; the disclosures of which are incorporated herein by references.) However, the coating layers produced by the sputtering processes are typically very thin, 1 micron or less in thickness. These coatings may not adhere well to the substrate and the various sputtering process have very slow deposition rates.

Metallic glass coating layers can be produced from amorphous metal powder by cold spray or kinetic energy processes. (See, e.g., A. List, et al., Journal of Thermal Spray Technology, 24, 108-118, 2015; U.S. Pat. No. 8,778,460 B2 to J. C. Farmer; the disclosures of which are incorporated herein by references.) However, amorphous metals may not be ductile enough to deform on impact with the substrate to make suitably high density and pore free coating layers, leading to porous and rough coatings. Particles may also rebound off the substrate or previously deposited layers instead of adhering, resulting in an inefficient coating process.

Laser based processes have attempted to fabricate metallic glass coatings. During direct energy deposition (DED) and/or laser cladding, powder is accelerated to a substrate where a laser provides the necessary heat to fuse the powder to the substrate or previous layers. (See, e.g., N. Sohrabi, et al., Surface and Coatings Technology, 400, 126223, 2020; A. Malachowska, et al., Surface and Coatings Technology, 405, 126733, 2021; L. Zhai, et al., Scientific Reports, 9, 17660, 2019; the disclosures of which are incorporated herein by references.) In principle, coatings with an amorphous structure can be produced by DED or laser cladding. However, the raster scanning of laser based processes can lead to slow deposition rates and also reheats previously deposited amorphous coating layers. Successive reheating of the amorphous layers can trigger crystallization in the the heat affected zone. The coating layers produced by DED and/or laser cladding can contain cracks and pores from poor fusion as well as having rough and wavy surfaces.

Immersion coating techniques of metallic glass-based materials have difficulty to achieve an even coating thickness although the coating layers may be smooth. (See, e.g., U.S. Pat. No. 9,211,564 B2 to Hofmann et al.; the disclosure of which is herein incorporated by reference in its entirety.) An object is coated with a layer of metallic glass-based material using immersion coating techniques described in U.S. Pat. No. 9,211,564 B2. A cross section of a coated object using immersion coating techniques in accordance with an embodiment of the invention is illustrated in FIG. 1 . The object (104) is coated with a layer of the metallic glass-based material (101). The metallic glass-based layer (101) completely covers the object (104). However, the thickness of the metallic glass-based layer is uneven. As can be seen, the thickness of the metallic glass-based layer at position 102 and position 103 are irregular. The thickness of the metallic glass-based coating at position 102 is about 79 microns and the thickness at position 103 is about 20 microns, giving a minimum flatness of about 59 microns.

Metallic glass-based coating layers using immersion coating techniques described in U.S. Pat. No. 9,211,564 B2 exhibit coating waviness and thickness irregularity. Coating waviness and thickness irregularity of an object coated with a layer of metallic glass-based material using immersion coating techniques in accordance with an embodiment are illustrated in FIG. 2A and FIG. 2B. FIG. 2A illustrates a surface of an object coated using immersion coating techniques. The coated object surface appears to be uneven and wrinkled. FIG. 2B illustrates a 3D representation of a wrinkled portion of the immersion coated object. The wrinkled surface of the coated layer has a height variation of about 69 microns, giving a minimum flatness of 69 microns. FIG. 2A and FIG. 2B show that immersion coated objects have a wavy surface and uneven thickness of the coating layer.

Many embodiments provide coating processes including (but not limited to) conduction quench coating to apply a layer of even and thick coating of metallic-glass based materials on at least a portion of an object. Many embodiments provide heating and conduction quench cooling processes during the fabrication of metallic-glass based materials. In several embodiments, coating materials including (but not limited to) metallic glass forming alloy can be deposited on the object to be coated. Heating can be applied to the coating materials to form liquid phase of the metallic glass forming alloy in accordance with some embodiments. In certain embodiments, conduction quench cooling can be applied to the coating materials as soon as the heating process is completed to form a solid phase metallic glass coating. The solid phase metallic glass in accordance with many embodiments has a surface that is smoother than a surface of the object to which the metallic glass forming alloy is applied.

Several embodiments provide that properties of metallic glass coating layers including (but not limited to) bonding to the substrate, porosity, roughness, and flatness, can be controlled and optimized during the conduction quenching cooling processes to produce desired metallic glass layers. In some embodiments, the force and/or the velocity of the conduction quenching apparatus can be optimized to control the thickness and/or smoothness of the coating layers, the adhesion between the coating layers and the object, and ensure good thermal contact with the molten metallic glass liquid. Many embodiments provide that crystalline microstructures of coating layers can be controlled by the quenching apparatuses. Quenching rate and/or applied pressure of the quenching apparatuses can produce coating layers of fully amorphous, amorphous and crystalline, and fully crystalline microstructures. In certain embodiments, applied pressure by the quenching apparatuses can reduce and/or remove porosity.

Some embodiments provide that the metallic-glass based coating layers have a uniform thickness throughout the coating layer. In certain embodiments, the metallic-glass based coating layers have a uniform thickness ranging from about 1 micron to about 1 mm. In several embodiments, the coating thickness may range from about 5 microns to about 100 microns. The metallic glass coating layers in accordance with some embodiments are smooth and have no wrinkling. In several embodiments, surface roughness of the metallic-glass coating layers can range from about 0.020 micron Ra to about 250 micron Ra.

Systems and methods for fabricating metallic glass-based materials with uniform and even thickness using conduction quench cooling processes in accordance with various embodiments of the invention are discussed further below.

Conduction Quench Cooling Processes

Many embodiments provide conduction quench cooling processes to fabricate uniform and even metallic glass-based materials including (but not limited to) coating layers. A method for applying a layer of metallic-glass based coating in accordance with an embodiment of the invention is illustrated in FIG. 3 . The process 300 can begin by applying a layer of a metallic-glass forming alloy to at least a portion of an object (301). In a number of embodiments, metallic-glass forming alloy materials adhere to the portion of an object that is to be coated. Many embodiments provide an even coating of metallic-glass forming alloy materials to the object, and the coating has a uniform thickness. In many embodiments, the metallic-glass forming alloy can have crystalline and/or amorphous structure. Several embodiments include that metallic-glass forming alloy can be prepared in a controlled atmosphere. In some embodiments, the controlled process can be carried out in full vacuum. In certain embodiments, metallic-glass forming alloy can be prepared in a vacuum chamber where oxygen is removed and the chamber is backfilled with an inert gas including (but not limited to) argon (Ar). Several embodiments provide that the metallic glass forming alloys have a composition that is able to form amorphous metallic glass. Examples of metallic-glass forming alloy elements include (but are not limited to): Zr, Ti, Cu, Al, Nb, Pt, Pd, Au, Ni, Fe, Mg, Ce, La, Be, P, C, B and their combinations thereof. Examples of metallic glass forming alloy include (but are not limited to): Zr_(52.5)Ni_(14.6)Al₁₀Cu_(17.9)Ti₅, Zr₅₇Cu_(15.4)Ni_(12.6)Al₁₀Nb₅, Zr₅₇Cu_(15.4)Ni_(12.8)Al_(10.3)Nb_(2.8), Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅, Zr_(41.2)Ti_(13.8)Ni₁₀Cu_(12.5)Be_(22.5), Zr₆₅Cu₁₈Ni₇Al₁₀, Zr₂₀Cu₂₀Hf₂₀Ti₂₀Ni₂₀, Cu₄₃Zr₄₃Al₇Be₇, Zr₄₃Cu₄₃Al₇Ag₇, Cu₄₇Zr₄₆Al₄Y₂, Ni_(68.6)Cr_(8.7)Nb₃P₁₆B_(3.2)Si_(0.5), Ni₅₃Nb₂₀Ti₁₀Zr₈Co₆Cu₃, Ti₄₁Zr₂₅Be₂₈Fe₆, Ti_(37.31)Zr_(22.75)Be_(25.48)Fe_(5.46)Cu₉, Zr₅₀Cu₃₇Al₁₀Pd₃, Zr₆₅Al_(7.5)Ni₁₀Pd_(17.5), Zr₆₅Cu_(17.5)Ni₁₀Al_(7.5), Zr₅₃Co_(17.5)Ni_(12.5)Al_(12.5)Ti_(4.5), Fe_(49.7)Cr_(17.7)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2.4), Fe₄₁Co₇Cr₁₅Mo₁₄Y₂C₁₅B₆, Pt_(57.5)Cu_(14.7)Ni_(5.3)P_(22.5), Pd₄₀Cu₃₀Ni₁₀P₂₀, Pd_(42.5)Cu₃₀Ni_(7.5)P₂₀. As can readily be appreciated, any of a variety of metallic-glass forming alloy compositions can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

In many embodiments, the object that is to be coated with metallic-glass may have a melting temperature at least higher than the melting temperature of the metallic-glass forming alloy. The object can be made of metal and/or ceramic. Examples of materials the object can be made of include (but are not limited to): steel, stainless steel, titanium, iron, copper, aluminum, nickel, cobalt, and graphite. In some embodiments, metallic-glass forming alloy comprising majority Zr, Ti, Ni, and/or Cu may have a melting temperature of 800° C. or higher, hence an object made of aluminum, with melting temperature of about 660° C., may not be applicable. In certain embodiments, metallic-glass forming alloying comprising majority Pd, Pt, Au, Ca, and/or La may have a melting temperature less than 600° C., and object made of aluminum, with melting temperature of about 660° C., can be coated with such metallic-glass forming alloy. As can readily be appreciated, any of a variety of object material compositions can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention. Several embodiments provide that the metallic-glass forming alloys and the alloys the objects are made of may be able to grow a beneficial diffusion reaction layer that can make a strong bond between the coating substrate and metallic glass coating.

Some embodiments include that the metallic glass forming alloy can be in piece forms including (but not limited to) foils, sheets, powders, particles, granules, ribbons, and chunks. In many embodiments, foils, sheets, and/or ribbons of metallic glass forming alloy can produce uniform and even metallic glass-based layers better than powders and/or particles forms. Powder form of metallic-glass forming alloy may improve adhesion to the object surfaces and create an even coating. In some embodiments, powder and/or particle forms of metallic-glass forming alloy can help to control total amount of metallic-glass forming alloy applied on the surface of the object. The total weight and/or the total thickness of the metallic glass forming alloy powders and/or particles may determine the thickness of the coating layers. Many embodiments include that the diameters of metallic-glass forming alloy particles are at least about 10 microns. In some embodiments, the diameters of particles range from about 10 microns to about 200 microns. Certain embodiments use unsieved powder of Zr-based metallic-glass forming alloy. As can readily be appreciated, any of a variety of metallic glass forming alloy forms can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

In several embodiments, metallic-glass forming alloy pieces can be mixed with a carrier liquid to form an easy to use slurry before applying to the object. A number of embodiments use carrier liquids that can evaporate in order to leave behind a layer of metallic-glass forming alloy particles on the surface of the article to be coated. The liquids are chosen such that after they evaporate there is no residue left behind that could affect the glass forming ability of the metallic-glass forming alloy. Some embodiments use clean distilled water as a carrier liquid. Several embodiments use organic solvents as the carrier liquid, including (but not limited to) ethanol, methanol, isopropanol, and acetone. Mixing the metallic-glass forming alloy particles with a carrier liquid can improve the flow of the material so it can easily cover the part of the object to be coated evenly. The density of the layer of applied metallic-glass forming alloy may depend on the packing factor of the particles after the carrier liquid evaporates. In several embodiments, foils, sheets, and/or ribbons of metallic-glass formed alloy may not need to dissolve in a solvent before applying to the object.

The metallic-glass forming alloy can be applied to the object at room temperature ranging from about 20° C. to about 25° C. in accordance with certain embodiments. Many embodiments aim to avoid applying excess metallic-glass forming alloy to the object. In some embodiments, metallic-glass forming alloy powder mixed with liquid carriers can be allowed to flow to coat the object because of the carrier liquid making it into a spreadable slurry. In certain embodiments, metallic-glass forming alloy powder can be dissolved in inorganic and/or organic solvents to form a spreadable slurry. Once the slurry is made, it can be scooped up and put on the surface by hand and then spread around evenly with spoons and/or spatulas. In several embodiments, metallic-glass forming alloy slurry can be placed in a dispensing device including (but not limited to) a pipette to coat the object. In certain embodiments, a mask where the metallic-glass forming alloy slurry can be pushed over to coat the object may be used. Several embodiments implement using metallic-glass forming alloy in the forms of foils, sheets, and/or ribbons as the coating source material. The foils, sheets, and/or ribbons can be cut out to match the shape of at least the portion of the object (such as a circular shape and/or any flat surface) to be coated and then placed on the object in accordance with some embodiments.

In a number of embodiments, masking dies can be used to prevent the metallic-glass forming alloy materials from covering portions of the object that are not to be coated. Some embodiments implement a masking die surrounding an object to prevent metallic-glass forming alloy materials adhering to the edges. In several embodiments, processes including (but not limited to) spinning can be used to create an even coating of metallic-glass forming alloy materials. Many embodiments provide that the masking dies can be made of a material that is non-reactive with the metallic-glass forming alloy and/or the carrier fluid. In some embodiments, the masking dies can be made of plastic including (but not limited to) PE, HDPE, PMMA, PP, PET, PEEK, and PVC. In several embodiments, the masking dies can be made of metal including (but not limited to) aluminum, steel, stainless steel, titanium, or copper. In certain embodiments, non-stick coating and/or paint that is not reactive with the solvent can be applied to the masking dies. In a number of embodiments, non-stick coating and/or paint that can repel the carrier fluid can be applied to the masking dies. As can readily be appreciated, any of a variety of methods to apply metallic-glass forming alloy materials to portions of an object can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

Metallic-glass forming alloy layers can be heated up to at least above the melting temperature of the metallic glass forming alloy (302). In many embodiments, the object with portions coated with metallic-glass forming alloy layers can be moved to a die to be heated. In several embodiments, heating platforms including (but not limited to) induction heating coils can be used for heating objects that are to be coated. In several embodiments, when induction heating is applied on metal objects, the heating die should couple to the electromagnetic field of the induction coil. Objects that are too small to be heated evenly may need to be placed in a heating die before they are placed on the heating platforms in accordance with some embodiments. When the objects are too small to couple directly to the induction coil and/or are made of materials that do not and/or weakly (such as ceramics) couple to an induction coil, a heating die can be used as the electromagnetic susceptor that will couple directly to the electromagnetic field of the induction coil. When the objects are large enough to couple to the induction coil and/or are made of strongly-coupling materials, the heating die may not couple to the coil, the die can be used for masking ability. Several embodiments use an induction coil where the heating platform does not actually supply any heat and acts as a platform to keep the die and/or object off of the conduction quenching blocks. Examples of strongly-coupling heating die materials include (but are not limited to): iron, steel, nickel, titanium, cobalt, tungsten, and graphite. In certain embodiments, when the object might be large and can couple to the heating coil directly, the die could be made of weakly-coupling materials. Examples of weakly-coupling materials include (but are not limited to): alumina, zirconia, silica, magnesia, sialon, silicides, and carbides. As can readily be appreciated, any of a variety of heating dies can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

Many embodiments provide that the heating die can also act as masking die that may prevent excess molten metallic glass forming alloy liquid from covering and/or coating the portions of the object that are not to be coated. A die material that does not wet with the metallic-glass forming liquid would be advantageous as it would make it easier to release the coated object from the die. The heating die could provide stable heating in accordance with several embodiments. In a number of embodiments, the heating die can also act as a mask to the molten metallic-glass forming liquid, preventing it from flowing to areas that are not intended to be coated. In some embodiments, the die can be made of strongly-coupling heating die materials and sprayed with a ceramic powder to prevent the heating die from reacting with the object. Examples of ceramic powders include (but are not limited to) BN, Al₂O₃, Zr₂O₃, or Y₂O₃. Many embodiments provide that the thermal expansion coefficient of the heating die/mask might need to match to the thermal expansion of the object to be coated. Matching thermal expansion coefficients would enable a controlled distance/gap between the masking aspect of the heating die and the coated object when the object and the die are heated up in tandem.

In certain embodiments, the heating die and object can be moved on to a heating platform. The heating platform can be suspended above the conduction quenching block. In many embodiments, a second conduction quenching block can be suspended above the heating platform. In several embodiments, the conduction quenching blocks can be made of (but not limited to) copper, brass, stainless steel, or steel. In some embodiments, the heating platform may be raised off the conduction quenching block by a moving mechanism including (but not limited to) a spring. Being kept away from the heating platform, the conduction quenching block can stay cool and away from the heating platform. In certain embodiments, the conduction quenching blocks may be temperature controlled by a recirculating liquid including (but not limited to) water or oil. Many embodiments provide that the metallic-glass forming alloy layers adhered to the object and/or the heating die can be heated directly with a heating source to at least above the melting temperature (T_(m)) of the metallic glass forming alloy to melt the alloy. In many embodiments, the metallic-glass forming alloy can be heated to at least 150° C. above the T_(m)/liquidus. In several embodiments, the heating source including (but not limited to) induction heating coil, resistive heating furnace, heating lamp, laser, electron beam, combustion flame, electrical spark, and microwave plasma, may be a part of the heating platform. Certain embodiments may use a resistive heating furnace method. As can readily be appreciated, any of a variety of heating methods can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention. Several embodiments implement a controlled heating rate during the heating process for controlling the final temperature. In some embodiments, the total heating time can range from about 10 seconds to about 10 minutes. Some embodiments provide a heating rate of about 250° C. per minute, where a total heating time is around 4 minutes with an estimated final temperature from about 900° C. to about 1000° C. Many embodiments include that heating rate and total heating time may have more effect on the object materials than the metallic-glass forming alloy. As can readily be appreciated, any of a variety of heating parameters can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

Metallic-glass forming alloy layers can be cooled to form solid phase metallic glass (303). Many embodiments provide quenching liquid phase metallic glass to form solid phase metallic glass layers of coating. In many embodiments, conduction quenching blocks above and below the heating platform can quench the heated metallic-glass forming alloy layers simultaneously. Several embodiments provide that the conduction quenching blocks, the heating platform, and the object can be aligned along the center. The contact from the conduction quenching blocks may turn the metallic glass liquid into a solid coating, certain embodiments provide that the conduction quenching blocks can have the shape of the portion of the object where the coating is to be applied. The moveable mechanism connecting the heating platform and the conduction quenching block can be pushed down during the quenching step to cool the object and/or the heating die from the back side in accordance with some embodiments. Several embodiments provide that quenching can flatten the wrinkling of the metallic-glass forming alloy layers to achieve a smooth and uniform thickness coating. In some embodiments, the conduction quenching blocks can be temperature controlled by a recirculating heat transfer fluid, including (but not limited to) water or thermal oil. Some embodiments include that quenching by conduction quenching blocks (such as Cu blocks, but not limited to Cu) from two sides could enable faster cooling rates compared to a single side conduction including (but not limited to) on a non-moving platform. Additional embodiments contain that the number and orientation of the quenching blocks can be adapted to provide suitable quenching on any variety of shapes of objects to be coated, such as a combination of bottom, side, and top conduction quenching blocks. Some exemplary embodiments may provide that the temperature control of the conduction quenching blocks can be implemented on either the top or bottom block individually or both simultaneously. Certain embodiments implement quenching methods including (but not limited to) gas quenching, dipping in water, dipping in oil, dipping in very low melting point metals including (but not limited to) tin for different object geometries. As can readily be appreciated, any of a variety of quenching methods and geometries to cool liquid metallic-glass to form solid phase metallic glass can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

In many embodiments, the metallic glass has a relatively low critical cooling rate. A ‘critical cooling rate’ refers to how fast a liquid phase metallic glass must be cooled in order to form the corresponding solid phase metallic glass, i.e., in an amorphous crystalline structure. The critical cooling rate of a metallic glass is associated with its ‘glass forming ability’, a term that references a measure as to how easy it is to form a solid phase metallic glass. It is desirable to use a metallic glass having a low critical cooling rate in conjunction with embodiments of the invention because relatively substantial volumes of liquid phase metallic glass are used to coat the object in many embodiments, e.g. a sufficient quantity such that a smooth coating layer surface can result. Thus, with these substantial volumes, or large objects to be coated, it can become difficult to ensure a sufficiently high cooling rate such that a solid phase metallic glass can result using conventional cooling processes. However, by using a metallic glass composition that has a relatively low critical cooling rate, a solid phase metallic glass layer can form in spite of the volume of the liquid phase metallic glass applied, or the size of the object to be coated. In many embodiments, the critical cooling rate of the metallic glass alloy is less than approximately 1000 K/s. Although a particular threshold value is referenced, any suitable metallic glass can be implemented in accordance with embodiments of the invention.

Many embodiments provide that the conduction quenching blocks should be moved at a minimum amount of force and/or velocity to ensure a good thermal contact with the molten metallic glass liquid such that the coating can be quenched appropriately to achieve the desired coating layer structures. A poor thermal contact may result in a low heat transfer coefficient and thus low heat flux and cooling rate. A high heat transfer coefficient can result in a higher heat flux and higher cooling rate. If the conduction quenching blocks move too fast or press too hard on coming in to contact with the sample, the molten liquid may be pushed off of the surface or disrupted to the extent that the coating thickness, flatness, and/or roughness of the coating is negatively impacted. In several embodiments, the heating platforms may be held up and off of the bottom stationary quenching block, either by a spring or other moving mechanism. The force from the top moving quenching block may press the heating platform down on to the bottom quenching block to increase the overall cooling rate of the object on the heating platform.

In many embodiments, the quenching rate may depend on the properties of the portion of the object to be coated including (but not limited to) thickness, thermal diffusivity, and mass. The larger the portion, the more total heat that may need to be removed. In some embodiments, the cooling rate is faster than 1000° C./sec. As can readily be appreciated, any of a variety of cooling parameters can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention.

In a number of embodiments, thickness may be controlled with the pressing force and/or the velocity of the quenching block. Several embodiments include that the coating layer thickness can range from about 1 micron to about 1 mm. In certain embodiments, the heating die/mask can act as a reservoir to keep the molten metallic-glass forming alloy on the top layer to achieve a thick coating of up to 1 mm in thickness. In several embodiments, the coating thickness may range from about 5 microns to about 100 microns. In a number of embodiments, a spinning process can enable a thin coating layer of about 1 to 5 microns.

Several embodiments provide that the coating thickness may also depend on the speed at which the metallic glass liquid is quenched in to a solid. As the temperature of the metallic glass liquid drops, the viscosity of the liquid increases exponentially until it becomes solid at the glass transition temperature. Many embodiments provide that the materials that the conduction quench blocks are made of and/or the temperature of the conduction quench blocks may impact the liquid wetting behavior, heat transfer coefficient, and cooling rate of the coating. If the block has a low thermal conductivity/diffusivity (or high temperature), the metallic glass liquid may solidify slower. In this case, the velocity and force with which the conduction quench blocks are pressed may have a higher impact on the final coating thickness as the metallic glass liquid is fluid for a longer period of time. If the block has a high thermal conductivity/diffusivity (or low temperature) and makes good thermal contact with the liquid, it may be less relevant how hard or fast the conduction quench blocks are moved, as heat is being removed from the liquid at such a fast rate that the liquid may become a solid faster than the pressing force/velocity of the conduction quenching block can move/disturb the liquid.

The metallic glass coated object and/or the heating die can be removed from the heating platform after quenching in accordance with many embodiments. In several embodiments, the object can be removed/snapped away from the die rather easily. One possible concern may be the potential for bonding/adhesion of the object to the heating die due to the metallic glass liquid wetting both surfaces and joining them like a soldering/brazing process. However, because only a small amount of metallic glass forming alloy is intentionally applied in accordance with some embodiments, there should not be too much excess liquid metallic glass like in immersion/pouring processes. Additional embodiments provide that a refractory compound can be applied to the object or holder to prevent wetting of the liquid metallic glass to the holder.

Many embodiments provide uniform thickness of metallic glass layers applied by conduction quench techniques. A cross section of metallic glass coated object using conduction quench cooling process in accordance with an embodiment of the invention is illustrated in FIG. 4 . The object coated in FIG. 4 is a similar object used in FIG. 1 . FIG. 4 illustrates uniform thickness coating on the coated sample. The thickness of the metallic glass layer is about 70 μm. In comparison, the immersion coated object in FIG. 1 shows irregular thickness in the coating layer varying from 20 to 80 microns. The metallic glass layer coated with conduction quench techniques is thick, flat, and smooth compared to the one made with the immersion process as shown in FIG. 1 and FIGS. 2A-2B.

In many embodiments, adhesion and smoothness may be controlled with the pressing force and/or the velocity of the quenching block. The metallic glass coating has good smoothness and no wrinkling because of the applied pressure during quench step in accordance with some embodiments. Several embodiments include that surface roughness may be controlled by the conduction quenching blocks. Many embodiments achieve a metallic-glass coating layer with surface roughness that can match the surface roughness of the quenching block. In several embodiments, surface roughness of the metallic-glass coating can range from about 0.020 micron Ra to about 250 micron Ra. A number of embodiments include that the conduction quenching blocks could impart desired features including (but not limited to) molding geometries and/or features of the quenching block to the coating itself. Several embodiments provide that object with a rough surface may help with adhesion with the metallic glass coating layers as there may be more surface area for the bonding to take place. This increased substrate roughness may add bonding strength by introducing mechanical interlocking between the coating and substrate.

Some embodiments implement conduction quench techniques to coat objects of various geometries including (but not limited to) cylinder, annulus, and plate. In several embodiments, a 1 inch by 1 inch plate is coated with a metallic glass layer using conduction quench methods, which exhibits better amorphous character and uniform coating thickness compared to plates quenched with gas. This is due to the heat removal efficient thermal contact of the two-sided conduction quenching method compared to the turbulent and heat removal inefficient aspect of quenching with gas.

In many embodiments, devitrified metallic glass coating layers can be formed with conduction quench techniques. In several embodiments, low melting point non-metallic glass forming compositions coating layers can also be formed with conduction quench techniques.

While various processes for fabricating metallic glass-based materials using conduction quench cooling processes are described above with reference to FIG. 3 and FIG. 4 , any of a variety of processes that utilize conduction quench cooling to fabricate layers of metallic glass-based materials can be utilized in applying coating as appropriate to the requirements of specific applications in accordance with various embodiments of the invention. Systems for conduction quench cooling systems in accordance with various embodiments of the invention are discussed further below.

Conduction Quench Cooling System

Many embodiments provide conduction quench coating systems that can be used to fabricate metallic glass-based materials. An object to be coated for at least a portion can be placed on a holder. Some embodiments implement conduction quench processes to coat objects of various geometries including (but not limited to) cylinder, annulus, and plate. The object holder can be placed on a heating platform including (but not limited to) a heating block. In some embodiments, the heating platform can be placed above a cooling platform. Several embodiments provide that the heating platform can be placed below a second cooling platform. In certain embodiments, the heating platform can be aligned in the center with the conduction cooling platforms including (but not limited to) a quench block. A conduction quench coating system in accordance with an embodiment of the invention is illustrated in FIG. 5A. An object (503) can be placed on a holder (502). The holder and the object can be placed on a heating platform (504). The heating platform (504) is aligned in the center with a cooling platform (501). The cooling platform (501) can be above the heating platform (504) and the object (502) and not touching. A second cooling platform (505) can be below the heating platform to expedite cooling.

In many embodiments, the metallic-glass forming alloys with crystalline and/or amorphous structures can be processed to form the metallic glass-based coating layers. Some embodiments provide that the metallic glass forming alloys can be in forms including (but not limited to) foils, sheets, powders, particles, granules, ribbons, and chunks. Certain embodiments provide that metallic glass forming alloy foils, sheets, and/or ribbons, can form a more uniform coating layers than metallic glass forming alloy powders and/or particles. Some embodiments provide that metallic-glass forming alloys can be coated only on the portion of the object that needs to be coated. In several embodiments, foils of metallic-glass forming alloys can be overlaid on at least a part of an object to be coated. A conduction quench coating system in accordance with an invention is illustrated in FIG. 5B. At least a portion of the object (503) can be coated with a metallic-glass forming alloy. The object (503) can be coated before being placed on the holder (502). The object can also be placed on the holder first and then coated.

Several embodiments provide that the coated object can be heated on the heating platform to at least above the melting temperature of the metallic-glass forming alloys. The heating process in accordance with certain embodiments can be provided by a heating unit. A conduction quench coating system with a heating process in accordance with an invention is illustrated in FIG. 5C. A heating unit (506) can be placed to heat the object with at least a portion coated with the metallic-glass forming alloy (503) and the holder (502). A power source (not shown) can be supplied to the heating unit to produce the heat. The metallic-glass forming alloy can be heated to at least above the melting temperature.

Several embodiments provide that as soon as the metallic-glass forming alloy is melted, the aligned cooling platform can be brought in contact with the object to enable rapid cooling and formation of metallic glass-based coatings. As the cooling platform is aligned with the heating platform in the center, the heated object and/or the heating platform may not need to be moved around for the cooling processes. Once the metallic-glass forming alloy on the object is melted, the cooling processes can begin. In many embodiments, the cooling rate can be controlled to form various microstructures of the metallic glass-based coating layers including (but not limited to) fully amorphous, amorphous and crystalline, and fully crystalline. A conduction quench coating system with a conduction quench cooling process in accordance with an invention is illustrated in FIG. 5D. The aligned cooling platform (501) above the heating platform (504) can be brought to be in contact with the object coated with molten metallic-forming alloy (503) to cool the object. The second cooling platform (505) below the heating platform (504) can be turned on. The cooling platforms (501 and 505) are aligned along the center with the holder (502) and the heating platform (504). The holder (502) and the object (503) may not need to be moved upon cooling such that the conduction cooling process can take place as soon as the heating process completes. Little time loss between the heating and cooling process can ensure the formation of uniform coating layer with a desired thickness.

While various systems for conduction quench cooling are described above with reference to FIGS. 5A-D, any of a variety of systems that utilize conduction quench cooling to fabricate metallic glass-based materials can be utilized in applying coatings as appropriate to the requirements of specific applications in accordance with various embodiments of the invention. Processes for applying metallic glass forming alloy in accordance with various embodiments of the invention are discussed further below.

Conduction Quench Cooling Processes Using Foils of Metallic Glass Forming Alloy

Many embodiments provide that foils, sheets, and/or ribbons of metallic glass forming alloy can produce uniform and even metallic glass-based layers better than powders and/or particles forms. One advantage of foils, sheets, and/or ribbons over powders and/or particles may be that the foils, sheets, and/or ribbons are fully dense, while the same thickness of a layer of powders and/or particles may still have empty space inside because of the packing density of the powders and/or particles. Another advantage may be that foils, sheets, and/or ribbons have a lower total surface area where surface oxides can form. When melting the powders and/or particles, the metal may have been melted, but the surface oxides present on the powders and particles can remain unmolten, resulting in unwanted oxides in the coating. Alternatively, more complicated geometries would be easier to coat with a spray, paste, or slurry of powder or particles than a foil, sheet, or ribbon. Nevertheless, shaping the foils, sheets, and/or ribbons into a complicated shape is still possible by cutting or stamping followed by thermoplastic forming of the foils, sheets, and/or ribbons into the desired preform shape.

In many embodiments, the metallic-glass forming alloy can be applied to the object at room temperature ranging from about 20° C. to about 25° C. Several embodiments provide that the foils, sheets, and/or ribbons can be cut out to match the shape of at least the portion of the object (such as a circular shape and/or any flat surface) to be coated and then placed on the object. Pre-cutting the metallic glass forming alloy foils, sheets, and/or ribbons to have a similar shape of the object in accordance with many embodiments can enable a simpler and cleaner coating process. Pre-cutting may not be necessary, but it can help to minimize an excess amount of metallic glass forming alloy liquid when melting the alloy on the object. In several embodiments, foils and/or ribbons of metallic-glass formed alloy may not need to dissolve in a solvent before applying to the object.

Several embodiments provide that the total weight and/or thickness of the foils, sheets, and/or ribbons can relate to the total thickness of the coating. The total weight of starting materials that could potentially be made into a coating should be considered for the coating layer thickness. Many embodiments use metallic glass-forming alloy foils, sheets, and/or ribbons of various thickness ranging from about a few microns to about hundreds of microns. The foils, sheets, and/or ribbons of various thickness in accordance with certain embodiments can be quenched to form coating layers. To make a coating layer of about 100 microns thick, some embodiments may use a single piece of foil of about 100 microns thick, or 2 stacks of foil of about 50 microns thick, or 4 stacks of foil of about 25 microns thick, or 10 stacks of foil of about 10 microns thick.

Many embodiments provide that the coating layers formed by conduction quench cooling processes may not have a coating thickness that is greater than the thickness of the amount of starting materials. Several embodiments provide that the coating layers formed by conduction quench cooling processes may achieve a final coating thickness that is thinner than the amount of starting material by pressing harder during the quenching step. This thinness in accordance with certain embodiments may not be from pressurizing/increasing the density of the metallic glass liquid as it solidifies but from pushing the excess liquid off the surface before it has a chance to solidify. Some embodiments provide that the masking dies may prevent metallic glass liquid from overflowing to parts of the object that are not to be coated. The masking dies could also prevent the quenching block from going any further in accordance with some embodiments, which can be a way to control the coating thickness. Several embodiments provide that the geometries of the masking dies may also contribute to the final thickness of the coating layers.

Many embodiments provide that metallic glass forming alloys in the form of foils, sheets, and/or ribbons, of various compositions can be used to form metallic glass coating layers. Examples of metallic glass forming alloy include (but are not limited to): Zr_(52.5)Ni_(14.6)Al₁₀Cu_(17.9)Ti₅, Zr₅₇Cu_(15.4)Ni_(12.6)Al₁₀Nb₅, Zr₅₇Cu_(15.4)Ni_(12.8)Al_(10.3)Nb_(2.8), Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅, Zr_(41.2)Ti_(13.8)Ni₁₀Cu_(12.5)Be_(22.5), Zr₆₅Cu₁₈Ni₇Al₁₀, Zr₂₀Cu₂₀Hf₂₀Ti₂₀Ni₂₀, Cu₄₃Zr₄₃Al₇Be₇, Zr₄₃Cu₄₃Al₇Ag₇, Cu₄₇Zr₄₆Al₄Y₂, Ni_(68.6)Cr_(8.7)Nb₃P₁₆B_(3.2)Si_(0.5), Ni₅₃Nb₂₀Ti₁₀Zr₈Co₆Cu₃, Ti₄₁Zr₂₅Be₂₈Fe₆, Ti_(37.31)Zr_(22.75)Be_(25.48)Fe_(5.46)Cu₉, Zr₅₀Cu₃₇Al₁₀Pd₃, Zr₆₅Al_(7.5)Ni₁₀Pd_(17.5), Zr₆₅Cu_(17.5)Ni₁₀Al_(7.5), Zr₅₃Co_(17.5)Ni_(12.5)Al_(12.5)Ti_(4.5), Fe_(49.7)Cr_(17.7)Mn_(1.9)Mo_(7.4)W_(1.6)B_(15.2)C_(3.8)Si_(2.4), Fe₄₁Co₇Cr₁₅Mo₁₄Y₂C₁₅B₆, Pt_(57.5)Cu_(14.7)Ni_(5.3)P_(22.5), Pd₄₀Cu₃₀Ni₁₀P₂₀, Pd_(42.5)Cu₃₀Ni_(7.5)P₂₀. As can readily be appreciated, any of a variety of alloy compositions can be utilized as appropriate to the requirements of specific applications.

Several embodiments provide that an object can be coated with metallic-glass forming alloy including (but not limited to) Zr_(52.5)Ni_(14.6)Al₁₀Cu_(17.9)Ti₅ metallic-glass forming alloy in powder form and in foil form. The sieved powder can have an average diameter of less than about 25 microns. The total weight of the powder used to coat the object can be about 18 mg. The foil can be cut out to have a similar shape as the object. The foil can be about 110 microns in thickness. The total weight of the foil can be about 33.5 mg. Some embodiments provide that the objects can be coated with metallic glass layer and then polished. In certain embodiments, the coated objects may not be polished.

Table 1 below includes coating thickness and flatness measurements of an uncoated polished object, a powder coated and unpolished object, a powder coated and polished object, a foil coated and unpolished object, and a foil coated and polished object. The coating layers of the powder coated and foil coated samples are applied using conduction quench cooling processes.

TABLE 1 Thickness and Roughness Measurement Coating Thickness Flatness (μm) (μm) Uncoated Polished — 3.3 Powder Unpolished 53.8 8.2 Powder Polished 45.6 2.8 Foil Unpolished 83.7 5.9 Foil Polished 59.8 8.1

Surface images of an object coated with metallic-glass forming alloy in the form of powder and foil in accordance with an embodiment of the invention is illustrated in FIGS. 6A-6C. FIG. 6A illustrates the surface of an uncoated polished object (601), the polished coating surface of an object coated with powder using conduction quench cooling processes (602), and the polished coating surface of an object coated with foil using conduction quench cooling processes (603). The foil coated object (603) appears to have a smoother and more defect free surface than the surface of the powder coated object (602). FIG. 6A is magnified about 100 times.

FIG. 6B illustrates a detailed polished coating surface of an object coated with metallic-glass forming alloy powder using conduction quench cooling processes. FIG. 6C illustrates a detailed polished coating surface of an object coated with metallic-glass forming alloy foil using conduction quench cooling processes. The foil coated object (FIG. 6C) appears to have a smoother and more defect free surface than the surface of the powder coated object (FIG. 6B). The powder coated object shows a number of voids (604) on the surface. Both FIGS. 6B and 6C are magnified about 300 times.

Cross section images of an object coated with metallic-glass forming alloy in the form of powder and foil in accordance with an embodiment of the invention is illustrated in FIGS. 7A-7D. FIG. 7A illustrates the cross section of an object coated with powder using conduction quench cooling processes. FIG. 7B illustrates the cross section of an object coated with foil using conduction quench cooling processes. The conduction quenching cooling processes produce coating layers with uniform thickness with both the powder and foil metallic-glass forming alloy.

FIG. 7C illustrates a detailed cross section of an object coated with metallic-glass forming alloy powder using conduction quench cooling processes. FIG. 7D illustrates a detailed cross section of an object coated with metallic-glass forming alloy foil using conduction quench cooling processes. The foil coated layer (FIG. 7D) is smooth and even, and shows no wrinkles or voids. The surface of the powder coated object (FIG. 7C) has a number of voids (701) on the top surface. Both FIGS. 7C and 7D are magnified about 1500 times.

While various processes for applying metallic glass forming alloy are described above with reference to FIGS. 6A-7D, any of a variety of coating processes that utilize conduction quench cooling to fabricate metallic glass-based coatings can be utilized as appropriate to the requirements of specific applications in accordance with various embodiments of the invention. Processes for post processing in accordance with various embodiments of the invention are discussed further below.

Post Processing

Many embodiments provide post processing including (but not limited to) polishing, oxidation, and/or heat treatment, can be applied to the metallic glass-based coating layers. The heat treatment oxidation processes in accordance with certain embodiments can change the color and/or the mechanical properties including (but not limited to) wear resistance, hardness, and coefficient of friction of the metallic glass-based coatings. A number of embodiments provide that oxidation processes can enhance wear resistance, increase hardness, and lower the coefficient of friction of the metallic glass-based coating layers. In certain embodiments, oxidation processes can be carried out at various temperatures and at various time duration. Some embodiments provide oxidation post processing can be carried out at a constant temperature near the glass transition temperature for at least 2 minutes. Many embodiments provide that oxidation post processing can be carried out at a constant temperature below the glass transition temperature, but lower processing temperatures require longer holding times. The coated objects may be polished or not before the oxidation processes. Several embodiments provide that object is coated with a metallic glass-based coating using conduction quench cooling process, polished, and oxidized for about 2 minutes can have medium gold color. In certain embodiments, object coated with a metallic glass-based coating using conduction quench cooling process, polished, and oxidized for about 4 minutes may have light to medium blue color. Some embodiments provide that object coated with a metallic glass-based coating using conduction quench cooling process, polished, and oxidized for about 8 minutes may have dark blue or black color.

Several embodiments provide that heat treatment oxidation processes may be able to improve the hardness of the metallic glass-based coatings. Vickers hardness measurement in accordance with an embodiment of the invention is illustrated in FIG. 8 . The Vickers hardness measurements are carried out with 5 indents on each sample. Object 801 is an uncoated sample with a lowest Vickers hardness of less than 350 HV. Object 802 is coated with a metallic glass-based coating using conduction quench cooling process and oxidized. Heat treatment can improve the Vickers hardness of coated objects. Object 803 is coated with a metallic glass-based coating using conduction quench cooling process and heat treated with about 2 minutes. Object 804 is coated with a metallic glass-based coating using conduction quench cooling process and heat treated with about 4 minutes. Object 805 is coated with a metallic glass-based coating using conduction quench cooling process and heat treated with about 8 minutes. The longer the heat treatment, the higher the Vickers hardness of the coated samples.

EXEMPLARY EMBODIMENTS

Although specific embodiments of systems and methods are discussed in the following sections, it will be understood that these embodiments are provided as exemplary and are not intended to be limiting.

Example 1: Conduction Quench Cooling Process

Many embodiments provide parameters used in a conduction quench cooling process. In several embodiments, coatings of metallic glass-based materials are applied on an object. An object holder can be cut from a plate with a waterjet or machined from various billet forms. A foil of metallic glass forming alloy with similar shape of the object can be prepared using water jet cutting or laser cutting.

Some embodiments provide sample preparation processes for coating. A small amount of ceramic refractory compound can be applied to the holder surfaces to prevent bonding with the object to be coated. The object to be coated is cleaned with alcohol and placed on the holder. A metallic glass forming alloy foil (e.g., Zr_(52.5)Ni_(14.6)Al₁₀Cu_(17.9)Ti₅) can be placed in contact with the object. The stack of holder, object, and metallic glass forming alloy are then placed and centered on the heating platform. The Cu block and heating platform can be centered inside the induction coil and aligned with the top Cu block. Aim the pyrometer to observe the sample temperature during the coating process.

Several embodiments provide parameters used during sample coating processes. The coating process chamber is evacuated with a vacuum pump to below 35 mTorr and backfilled with Ar two times to ensure an inert atmosphere. Turn on the temperature controlled water recirculation pump and check that the temperature and pressure are appropriate. Turn on the induction power unit.

Ramp up to the power percentage and hold times: e.g., start at 30% power and slowly increase power 10% every 30 seconds while monitoring the pyrometer temperature and checking for melting of the metallic glass forming alloy foil.

Lower the Cu conduction quench block on the object after the correct pyrometer temperature is achieved. Turn off the induction unit and wait 2 minutes until venting and opening the chamber.

Raise the Cu conduction quench block and remove the coated object from the heating platform and holder.

Doctrine Of Equivalents

As can be inferred from the above discussion, the above-mentioned concepts can be implemented in a variety of arrangements in accordance with embodiments of the invention. Accordingly, although the present invention has been described in certain specific aspects, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that the present invention may be practiced otherwise than specifically described. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive. 

What is claimed is:
 1. A method of fabricating metallic glass comprising: applying at least one layer of metallic glass forming alloy to at least a portion of an object; heating the at least one layer of metallic glass forming alloy to at least above the melting temperature of the metallic glass forming alloy; and cooling the at least one melted layer of liquid phase metallic glass to form a layer of solid phase metallic glass on the at least a portion of the object; wherein the cooling process is selected from the group consisting of: conduction quenching, gas quenching, dipping in water, dipping in oil, and dipping in molten tin.
 2. The method of claim 1, wherein the at least one layer of metallic glass forming alloy comprises at least one element selected from the group consisting of: Zr, Ti, Cu, Al, Nb, Pt, Pd, Au, Ni, Fe, Mg, Ce, La, Be, P, C, and B.
 3. The method of claim 1, wherein the object is made of a material with a higher melting temperature than the melting temperature of the metallic glass forming alloy.
 4. The method of claim 1, wherein the at least one layer of metallic glass forming alloy is in a form selected from the group consisting of: powder, particle, granule, chunk, foil, ribbon, and sheet.
 5. The method of claim 4, wherein the at least one layer of metallic glass forming alloy is cut to match the shape of the at least a portion of the object before applying.
 6. The method of claim 1, wherein the at least one layer of metallic glass forming alloy is heated to at least 150° C. above the melting temperature of the metallic glass forming alloy.
 7. The method of claim 1, wherein the heating is applied by a heating source selected from the group consisting of an induction heating coil, a resistive furnace, a heating lamp, a laser, an electron beam, a combustion flame, an electrical spark, and a microwave plasma.
 8. The method of claim 1, wherein the heating takes place on a heating platform comprising a heating block.
 9. The method of claim 8, wherein the heating block comprises a material selected from the group consisting of copper, brass, steel and stainless steel.
 10. The method of claim 8, wherein the conduction quenching is applied by at least one conduction quenching block, and the at least one conduction quenching block is aligned with the heating block in the center.
 11. The method of claim 8, wherein the conduction quenching is applied by two conduction quenching blocks; wherein a first conduction quenching block is above the heating block and not touching, and a second conduction quenching block is below the heating block; wherein the two conduction quenching blocks and the heating block are aligned in the center.
 12. The method of claim 1, wherein the cooling takes place immediately after the heating is complete.
 13. The method of claim 1, wherein the heating and cooling take place in vacuum.
 14. The method of claim 1, wherein the layer of solid phase metallic glass has a uniform thickness throughout the layer, and the thickness ranges from about 1 micron to about 1 millimeter.
 15. The method of claim 1, wherein the layer of solid phase metallic glass has a surface roughness ranging from about 0.020 micron Ra to about 250 micron Ra.
 16. The method of claim 1, wherein the layer of solid phase metallic glass has a microstructure selected from the group consisting of: fully amorphous, amorphous and crystalline, and fully crystalline.
 17. A system for fabricating metallic glass comprising: at least one heating platform; at least one sample holder on the at least one heating platform; and at least one cooling block above the at least one heating platform; wherein the at least one cooling block is not touching the at least one heating platform; wherein the at least one heating platform, the at least one sample holder, and the at least one cooling block are aligned in the center.
 18. The system of claim 17, further comprising a second cooling block below the at least one heating platform, wherein the second cooling block is in contact with the at least one heating platform.
 19. The system of claim 17, wherein the at least one heating platform comprises a heating block comprising a material selected from the group consisting of: copper, brass, and steel.
 20. The system of claim 17, wherein the at least one cooling block comprises a material selected from the group consisting of: copper, brass, and steel.
 21. The system of claim 18, wherein the second cooling block is cooled by water.
 22. The system of claim 17, wherein the at least one heating platform comprising a heating source selected from the group consisting of an induction heating coil, a resistive furnace, a heating lamp, a laser, an electron beam, a combustion flame, an electrical spark, and a microwave plasma. 